From ba25df8407c629eebb248f589532067f86e0b400 Mon Sep 17 00:00:00 2001
From: Thomas Schmucker <ts@its1.de>
Date: Tue, 17 Dec 2024 17:03:58 +0100
Subject: aoc 2024, day 17, part 1

---
 2024/src/day17.cpp | 110 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 110 insertions(+)
 create mode 100644 2024/src/day17.cpp

(limited to '2024')

diff --git a/2024/src/day17.cpp b/2024/src/day17.cpp
new file mode 100644
index 0000000..f0d1010
--- /dev/null
+++ b/2024/src/day17.cpp
@@ -0,0 +1,110 @@
+#include <fstream>
+#include <iostream>
+#include <map>
+#include <sstream>
+#include <string>
+#include <tuple>
+#include <vector>
+using namespace std;
+
+using program_type   = vector<unsigned long>;
+using registers_type = map<char, unsigned long>;
+
+vector<string>
+split(const string& line, char sep = ' ')
+{
+	vector<string> parts;
+	stringstream   input{ line };
+
+	for ( string part; getline(input, part, sep); ) {
+		parts.emplace_back(part);
+	}
+
+	return parts;
+}
+
+tuple<registers_type, program_type>
+read_file(string_view filename)
+{
+	fstream input{ filename };
+
+	map<char, unsigned long> registers;
+	vector<unsigned long>    program;
+
+	for ( string line; getline(input, line); ) {
+		if ( line.empty() ) {
+			continue;
+		}
+
+		const auto parts = split(line, ':');
+
+		if ( parts[0] == "Register A" ) {
+			registers['A'] = stoul(parts[1]);
+		}
+		else if ( parts[0] == "Register B" ) {
+			registers['B'] = stoul(parts[1]);
+		}
+		else if ( parts[0] == "Register C" ) {
+			registers['C'] = stoul(parts[1]);
+		}
+		else if ( parts[0] == "Program" ) {
+			for ( const auto& value: split(parts[1], ',') ) {
+				program.emplace_back(stoul(value));
+			}
+		}
+	}
+
+	return { registers, program };
+}
+
+void
+part1(const tuple<registers_type, program_type>& data)
+{
+	auto [registers, program] = data;
+
+	for ( unsigned long ip = 0; ip < program.size(); ) {
+		const auto opcode  = program.at(ip++);
+		const auto operand = program.at(ip++);
+		const auto value   = (operand < 4) ? operand : registers[char('A' + operand - 4)];
+
+		switch ( opcode ) {
+		case 0: // adv
+			registers['A'] >>= value;
+			break;
+		case 1: // bxl
+			registers['B'] ^= operand;
+			break;
+		case 2: // bst
+			registers['B'] = value % 8;
+			break;
+		case 3: // jnz
+			if ( registers['A'] != 0 ) {
+				ip = operand;
+			}
+			break;
+		case 4:
+			registers['B'] ^= registers['C'];
+			break;
+		case 5:
+			cout << (value & 7) << ',';
+			break;
+		case 6:
+			registers['B'] = registers['A'] >> value;
+			break;
+		case 7:
+			registers['C'] = registers['A'] >> value;
+			break;
+		default:
+			cout << "Error" << endl;
+			return;
+		}
+	}
+	cout << endl;
+}
+
+int
+main()
+{
+	auto data = read_file("data/day17.txt");
+	part1(data);
+}
-- 
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